/*
 * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
 * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
 * copyright and warranty notices given in that book:
 *
 * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
 *
 *
 * "The authors and publisher have taken care in the preparation of this book,
 * but make no expressed or implied warranty of any kind and assume no
 * responsibility for errors or omissions. No liability is assumed for
 * incidental or consequential damages in connection with or arising out of the
 * use of the information or programs contained herein."
 *
 * Permission is granted for this code to be used for educational purposes in
 * association with the book, given proper citation if and when posted or
 * reproduced.Any commercial use of this code requires the explicit written
 * permission of the publisher, Addison-Wesley Professional, a division of
 * Pearson Education, Inc. Send your request for permission, stating clearly
 * what code you would like to use, and in what specific way, to the following
 * address:
 *
 *  Pearson Education, Inc.
 *  Rights and Contracts Department
 *  75 Arlington Street, Suite 300
 *  Boston, MA 02216
 *  Fax: (617) 848-7047
*/

#include "Sales_item.h"
#include <iostream>
using std::istream;
using std::ostream;

// assumes that both objects refer to the same isbn
Sales_item& Sales_item::operator+=(const Sales_item& rhs)
{
	units_sold += rhs.units_sold;
	revenue += rhs.revenue;
	return *this;
}

// assumes that both objects refer to the same isbn
Sales_item
operator+(const Sales_item& lhs, const Sales_item& rhs)
{
	Sales_item ret(lhs);  // copy lhs into a local object that we'll return
	ret += rhs;           // add in the contents of rhs
	return ret;           // return ret by value
}

istream&
operator>>(istream& in, Sales_item& s)
{
	double price;
	in >> s.isbn >> s.units_sold >> price;
	// check that the inputs succeeded
	if (in)
		s.revenue = s.units_sold * price;
	else
		s = Sales_item();  // input failed: reset object to default state
	return in;
}

ostream&
operator<<(ostream& out, const Sales_item& s)
{
	out << s.isbn << "\t" << s.units_sold << "\t"
		<< s.revenue << "\t" <<  s.avg_price();
	return out;
}

double Sales_item::avg_price() const
{
	if (units_sold)
		return revenue / units_sold;
	else
		return 0;
}

